Flow control valve

ABSTRACT

A flow control valve, in particular in the form of an electromagnetic proportional directional flow control valve ( 1 ), having a valve housing ( 2 ), in which a control piston ( 3 ) is guided such that it can be displaced axially, which control piston ( 3 ) actuates at least one fluid-conducting connection ( 4 ) between a fluid inlet ( 5 ) and an outflow opening ( 6 ), wherein an actuator part, in particular an armature ( 8 ), which can be actuated by an actuator, in particular in the form of a proportional magnet, acts on the control piston ( 3 ), is characterized in that a pressure detecting piston ( 9 ) serves for the action of the actuator part on the control piston ( 3 ), in that the fluid inlet ( 5 ) is connected in a fluid-conducting manner by means of a pressure detecting channel ( 11 ) to a pressure detecting chamber ( 12 ) in such a way that the fluid pressure which prevails in the pressure detecting chamber ( 12 ) loads the pressure detecting piston ( 9 ) and the control piston ( 3 ) with a force (F) in the direction of relief of the actuator, and in that a further fluid-conducting connection ( 4 ′) between the fluid inlet ( 5 ) and a further outflow opening ( 6 ′) is actuated.

The invention relates to a flow control valve, in particular in the form of an electromagnetic proportional directional flow control valve, having a valve housing, in which a control piston is guided in such a way that it can be displaced axially, and said control piston actuates at least one fluid-conducting connection between a fluid inlet and an outflow opening, wherein an actuator part, in particular an armature, which can be actuated by an actuator, in particular in the form of a proportional solenoid, acts on the control piston.

Flow control valves, in particular in the form of electromagnetic directional flow control valves, have the function of setting the volume flow to a constant value independently of the pressure differential and the viscosity of a fluid. Depending on the design of the respective flow control valve, the volume flow can be controlled on the influent flow side or the return side of a connected hydraulic consumer. Flow control valves with adjustable volume flow can be implemented by means of proportional solenoids as the actuators in such a way that a proportional solenoid can produce a parallel shift of the characteristic of the valve concerned.

In this context, the volume flow is adjusted continuously by means of the proportional solenoid that is actuated by means of an electronic power amplifier. The proportional valves can be position controlled or force controlled. Usually, a control piston, which is designed as a sliding piston, acts, subject to the action of the magnetic force of the proportional solenoid, against a compression spring in such a way that an orifice cross section is correspondingly enlarged or decreased. The pressure independence of the volume flow is achieved by means of a differential pressure valve (pressure compensator), which provides a constant pressure differential at the metering orifice and is normally downstream of this metering orifice.

A directional valve having the aforementioned function is known from the prior art DE 196 04 317 A1. This valve has a hollow cone-shaped valve seat that forms a valve opening range with a valve element. In this case, the valve element has a spherical segmental section. The radius of the spherical segmental section and the opening angle of the hollow cone-shaped valve seat are established in such a way that a sealing region is formed, when the valve element sits on the valve seat. The valve element is guided in a movable manner in a valve body, with the valve body having a corresponding inner circumferential surface that has a more or less uniform diameter over the entire length of the valve element.

In particular, such flow control valves of a seat-type design have at least two problem areas. First of all, the power demand for the proportional solenoid is relatively high; and, secondly, such valves are difficult to actuate with a certain degree of precision in the extreme opening ranges. Hence, the electromagnetic directional valve, disclosed in the document, has a flat characteristic, so that the solenoid drive force is evened out in relation to an identical actuating current over almost the entire range of the valve stroke. This feature is implemented by setting the solenoid drive force in such a way that it has a flat characteristic in order to make the control of the valve opening degree easier. However, this feature has the drawback that the solenoid drive force is relatively high with respect to a change in a range, in which the current value is correspondingly large. This results from the relationship that the solenoid drive force is proportional to the square of the current value. Therefore, the magnitude of change in the solenoid drive force becomes larger in relation to the same magnitude of change in the current.

Therefore, the flow rate of a fluid to be controlled with such valves tends to change abruptly in relation to a small change in the actuating current in a range, in which the opening degree of the electromagnetic proportional flow control valve is small. Hence, such flow control valves of the seat-type design have the problem that it is difficult to achieve an accurate flow rate control in a range with a low flow rate, at which the flow rate to be controlled is low.

In contrast, the prior art flow control valves of the sliding valve type design generally have a non-minimized power demand and/or a non-minimized size of the proportional solenoid.

Based on this state of the art, the object of the present invention is to provide a flow control valve that makes possible a small overall size and, at the same time, a precise volume flow control over the entire anticipated operating range; and the energy demand of this flow control valve is minimized.

Such an object is achieved by means of a flow control valve having the features specified in claim 1 in its entirety.

The invention provides, according to the characterizing part of claim 1, that a pressure detecting piston serves for the action of the actuator part on the control piston; that the fluid inlet is connected in a fluid-conducting manner to a pressure detecting chamber by means of a pressure-detecting duct in such a way that the fluid pressure, which prevails in the pressure detecting chamber, applies a force to the pressure detecting piston and the control piston in the direction of a relief of the actuator; and that an additional fluid-conducting connection between the fluid inlet and an additional outflow opening is actuated. In total, such an approach provides an electromagnetically operable flow control valve that lends itself well as a 3-way proportional flow control valve to carrying out the volume flow control for at least two hydraulic consumers.

The pressure detecting piston of the flow control valve is loosely connected to the control piston; and, as a result, forces act on the pressure detecting piston in the direction of a relief of the proportional solenoid. In addition, the necessary actuating forces for the control piston are reduced, because its projection surface is decreased, compared to the known valves of the seat type design, in the fluid flow direction by means of the cross-sectional area of the pressure detecting piston that extends, as required, into the control piston. As a result, the flow control valve according to the invention has three design measures in the smallest space, first of all, to reduce the necessary actuating forces and, thus, the energy consumption for its valve element in the form of the control piston, that is, by the reverse action of the fluid flow on the pressure detecting piston through the application of fluid to the rear side of the pressure detecting piston in the pressure detecting chamber and the associated reduction of the influent flow and/or pressurized projection surface or end face of the control piston itself. Secondly, the flow control valve according to the invention has an additional fluid-conducting connection between its fluid inlet and an additional outflow opening, as a result of which volume flow control is made possible for two hydraulic consumers.

The flow control valve according to the invention provides an electromagnetically operable flow control valve, which has markedly flat characteristic curves, so that the solenoid drive force of the flow control valve is evened out in relation to an identical actuating current over the entire range of the valve stroke, as a result of which it is possible to achieve a characteristic of curves that is almost 100% linear.

The outflow openings in the valve housing are arranged in such an advantageous way that when the free flow cross section of the one outflow opening is enlarged due to a movement of the control piston, the free flow cross section of the respectively other outflow opening is decreased by means of the control piston. Preferably, the flow control valve is designed as a kind of priority valve such that the one outflow opening forms a media port in order to supply a connectable consumer of higher priority with a flowable medium; and, inversely, the other outflow opening forms an additional media port in order to supply a consumer of lower priority. The result of the design measures is a flow control valve in the manner of a priority valve having the smallest energy demand and a minimized installation space requirement.

In an especially preferred embodiment, the flow control valve is provided with a control piston with at least two rows of passage openings that are spaced axially apart from each other in such a way that one of the rows is assigned the one outflow opening; and a respective other row is assigned the other outflow opening. In total, the results are symmetrical flow patterns inside the flow control valve, in particular inside its control piston.

The passage openings and the outflow openings consist preferably of a plurality of rows of drill holes assigned to each other, which are axially spaced apart from each other relative to the longitudinal or actuating axis of the valve. The drill holes lie diametrically opposite each other in the respective row. In total, the results are symmetries in the flow control valve relative to its longitudinal axis, so that the fabrication of the flow control valve is simplified; and harmonic flow guides and flow transitions are achieved inside the valve body.

The control surfaces of the control piston, to which fluid pressure is effectively applied, and the control surfaces of the pressure detecting piston yield, when pulled away from each other, a remaining control surface, to which fluid pressure is applied and that introduces a force to the two pistons, so that the result is a relief for the proportional solenoid. Without the pressure detecting piston with its pressure-effective detecting piston rear side, all of the fluid pressure on the fluid inlet side of the valve would be available on the proximal front side of the valve element or the control piston, with the result that the proportional solenoid would have to generate very high actuating forces for the valve element, and respectively the control piston. This in turn would assume that the proportional solenoids inside the valve device were large in size and also had a correspondingly high energy demand.

The use of the pressure detecting piston serves to reduce, as explained, the necessary actuating forces, so that proportional solenoids that are small in size suffice for the actuating functions with a correspondingly low power demand. Moreover, the pressure detecting piston also supports the modular design of the flow control valve, because the valve components, including the proportional solenoid, can be installed in standardized size gradations, in order to be able to cover a wide range of performance classes of fluid or media flows to be controlled. It is surprising to the average person skilled in the field of valve engineering that he can significantly reduce now for the first time the actuating force of the proportional solenoid through the use of a pressure detecting piston and a fluid guide on its side facing the proportional solenoid.

A preferred embodiment of the flow control valve according to the invention provides that the respective pressure detecting duct produces a permanently fluid-conducting connection between the fluid inlet and the pressure detecting chamber. At the same time, one embodiment provides preferably that the pressure detecting duct at least partially, preferably completely, penetrates the pressure detecting piston in the axial direction; and an additional embodiment can provide that for this purpose the pressure detecting duct, arranged laterally in the valve housing, is guided past the control piston. In individual cases, it is conceivable to use such pressure detecting ducts also jointly with a valve construction.

A precise control and actuating characteristic for the flow control valve can be achieved, if, in a preferred embodiment, the pressure detecting piston penetrates the control piston in such a way that the pressure detecting piston defines a metering orifice with a passage opening of the control piston in the area of the free front side of the pressure detecting piston. Said metering orifice points in the direction of the fluid inlet side of the flow control valve.

In an especially preferred embodiment of the flow control valve according to the invention, the metering orifice is formed by means of the inner wall parts of the control piston; and said metering orifice may be found between the two outflow openings in any movement position of the control piston. In this context, the pressure detecting duct of the pressure detecting piston extends through the metering orifice so as to form a radial distance. When seen in the axial direction of the flow control valve according to the invention, the free front-side end of the pressure detecting duct empties into the other fluid-conducting connection between the fluid inlet and the other outflow opening in any movement position of the control piston.

In an additional especially preferred embodiment of the flow control valve according to the invention, the armature, which can be axially displaced by means of the proportional solenoid, does not act directly on the control piston, but rather the pressure detecting piston, which partially or totally penetrates the control piston in the axial direction, serves as a kind of intermediate member between the armature and the control piston. Said pressure detecting piston is actuated at least indirectly by the armature and is adjusted as a function of the measured pump pressure at the fluid inlet of the control piston and, thus, the opening cross section of the fluid-conducting connection. It is self-evident that the proportional solenoid with its armature can also be replaced with any other actuator with its actuator part, be it in the form of a hydraulic working cylinder actuation, be it in the form of an electric spindle drive, or the like. In such cases, the result is also a reduction in installation space and the energy required for the respective actuator system that is used.

The pressure detecting piston can be loosely connected to the control piston by means of a drive plate and, in particular, to the effect that the drive plate takes with it the control piston in the active direction of the energized proportional solenoid or a resetting device for the control piston, but that in any case it is possible to move both aforementioned pistons relative to each other in the opposite direction of movement of the armature of the proportional solenoid and the pressure detecting piston.

The proportional solenoid is designed advantageously in the manner of a “pushing magnet”; and when said proportional solenoid is in its non-energized state, the control piston is moved by means of a resetting device into a position in which the one fluid-conducting connection is blocked and the other fluid-conducting connection is at least partially opened. In an additional preferred embodiment, the proportional solenoid is designed in the manner of a “pulling magnet”; and when said proportional solenoid is in its non-energized state, the control piston is moved by means of a resetting device into a position in which the one fluid-conducting connection is at least partially open and the other fluid-conducting connection is blocked. Thus, a simple modification of just the proportional solenoid alone allows the inventive flow control valve in the manner of a priority valve to be produced as a “pushing magnet” or as a “pulling magnet” with two different kinds of switching positions in the non-energized state of the proportional solenoid.

In a preferred exemplary embodiment, the pressure detecting piston has a largest end face that is equal to preferably about one-fourth of the end face described by the control piston.

The pressure detecting piston widens in the diameter, preferably from its side facing the fluid inlet of the flow control valve to the side facing the armature. The control piston is designed, as stated above, as a sliding piston. In this case, a metering orifice opening, which faces the fluid inlet of the flow control valve, has preferably an inside diameter that is about twice as large as the diameter of the pressure detecting piston in this area.

The flow control valve according to the invention is explained in detail below by means of two basic exemplary embodiments with reference to the drawings. Referring to the diagrammatic drawings that are not drawn to scale:

FIG. 1 is to some extent a longitudinal sectional view and to some extent a view of a first exemplary embodiment of a flow control valve;

FIG. 2 is a representation of an additional exemplary embodiment of a flow control valve in a view comparable to that depicted in FIG. 1.

FIG. 1 shows the key components of an electromagnetically operable 3-way proportional flow control valve 1, which is capable of holding a hydraulic fluid volume flow from a hydraulic fluid pump (not illustrated) or any other pressure feed to at least one of two hydraulically connected consumers (not illustrated) more or less constant, independently of any pressure fluctuations that might occur. The electromagnetic 3-way flow control valve 1 can control the volume flow on the influent flow side or the return side of the hydraulic consumers (not illustrated), for example, in the form of working cylinders of a construction machine or the like.

The valve, hereinafter referred to only in short as the flow control valve 1, has a valve housing 2, which is configured as a screw-in cartridge solution. The lower, axial end of the valve housing 2 has a central fluid inlet 5 and a plurality of radial outflow openings 6, 6′, of which two are shown in pairs as drill holes in the longitudinal sectional view. A sleeve-shaped control piston 3, designed as a sliding piston, is guided such that, as a valve element, it can be displaced in a drill hole in the valve housing 2. The control piston 3 is held by a cylindrical or conical resetting device 17, designed as a compression spring, in the sense of a proportional solenoid, which is not shown in detail, on the other end of the valve housing 2. An actuator part of the proportional solenoid that is formed, in particular, as an armature 8, acts on the control piston 3 at its end facing the proportional solenoid.

A pressure detecting piston 9 serves for the actuator part to act on the control piston 3. The pressure detecting piston 9 connects the fluid inlet 5 to a pressure detecting chamber 12 by means of a pressure detecting duct 11. The resulting fluid pressure prevailing in the pressure detecting chamber 12 applies a force F to the pressure detecting piston 9 and the control piston 3 in the direction of a relief of the actuator. The flow control valve 1 has fluid-conducting connections 4, 4′ between the fluid inlet 5 and the outflow openings 6, 6′. When the free flow cross section of the outflow opening 6′ is enlarged in the control positions of the control piston 3, where the two outflow openings 6, 6′ are traversed by flow, the free flow cross section of the outflow opening 6 decreases.

The exemplary embodiment of the flow control valve 1, shown in FIG. 1 and also in FIG. 2, is designed in the manner of a priority valve, with an outflow opening 6 or 6′ forming a media port in order to supply a connectable consumer of higher priority with the fluid; and the other outflow opening 6′ or 6, respectively, can form relative to the former an additional media port in order to feed a consumer of lower priority. However, a different connection assignment with a correspondingly modified priority is also possible. In the exemplary embodiments shown in FIGS. 1 and 2, the respective outflow opening 6, 6′ is formed by a row of drill holes along the periphery of the valve housing 2. The control piston 3 in turn has at least two rows of axially spaced passage openings 19, 19′. In this case, the one row of the one outflow opening 6 and the respectively other row of the other outflow opening 6′ is assigned in each case a row of passage openings 19, 19′.

The result is the fluid-conducting connection 4 between the fluid inlet 5 and the row of drill holes relating to the outflow opening 6 and the fluid-conducting connection 4′ between the fluid inlet 5 and the row of drill holes relating to the other outflow opening 6′. In the exemplary embodiment depicted in FIGS. 1 and 2, the passage openings 19, 19′ and the outflow openings 6, 6′ consist most preferably of a plurality of rows of drill holes assigned to each other, which are axially spaced relative to the longitudinal or actuating axis of the valve 1 and are divided into rows. Depending on the movement position of the control piston 3, the passage openings 19, 19′ permit the passage of flowable medium or fluid into the respective fluid-conducting connection 4, 4′ or partially or totally block the respective fluid-conducting connection 4, 4′. In the aforementioned control positions of the control piston 3, the selected distances between the outflow openings 6, 6′ and the passage openings 19, 19′ allow a flowable medium to flow into both fluid-conducting connections 4, 4′ in predefinable amounts.

The control surfaces of the control piston 3, to which fluid pressure is effectively applied, and the control surfaces of the pressure detecting piston 9 yield, when pulled away from each other, a remaining control surface, to which fluid pressure is applied and that introduces a force to the two pistons 3, 9, so that the result is a relief for the proportional solenoid. This force relief allows the use of a proportional solenoid that is smaller in size than is the case in the prior art solutions that dispense with the pressure detecting piston 9 according to the invention. Furthermore, such a relief is energy saving, because the power consumption for the proportional solenoid is less. In this respect, the largest cross section of the pressure detecting piston 9 decreases the projection surface of the control piston 3; and the resulting remaining control surface leads to the force introduction that reduces the load on the proportional solenoid.

The pressure detecting duct 11 produces a permanently fluid-conducting connection between the fluid inlet 5 and the pressure detecting chamber 12. At the same time, the pressure detecting duct 11 penetrates the pressure detecting piston 9 in the axial direction. It can also be advantageous to arrange the pressure detecting duct 11 laterally in the valve housing 2 and to guide it past the control piston 3 (not illustrated). The control piston 3 is partially penetrated, as shown, by the pressure detecting piston 9 in the axial direction, so that the pressure detecting piston 9 defines a metering orifice 14 with a passage opening of the control piston 3 in the region of the free front side of said pressure detecting piston. The metering orifice 14 is formed by means of the inner wall parts of the control piston 3; and the metering orifice 14 may be found between the outflow openings 6, 6′ in any movement position of the control piston 3. In this context, the pressure detecting duct 11 of the pressure detecting piston 9 extends through the metering orifice 14 so as to form a radial distance. When seen in the axial direction of the flow control valve 1, the free front-side end of the pressure detecting duct 11 empties into the other fluid-conducting connection 4′ between the fluid inlet 5 and the other outflow opening 6′ in any movement position of the control piston 3. The armature 8, which can be axially displaced by means of the proportional solenoid, acts permanently on the control piston 3 by means of the pressure detecting piston 9, as an intermediate member. The pressure detecting piston 9 is loosely connected to the control piston 3 by means of a drive plate 13 in order to introduce a force to the control piston 3. The drive plate 13 is provided with an opening 18.

In FIG. 1, the flow control valve 1 is constructed with a proportional solenoid in the manner of a “pushing magnet,” so that when said proportional solenoid is in its non-energized state, the control piston 3 is moved by means of a resetting device 17 into a position in which the one fluid-conducting connection 4 is blocked and the other fluid-conducting connection 4′ is at least partially opened.

Then the control piston 3 opens and closes the fluid-conducting connections 4, 4′ by applying force to the armature 8 (also referred to as the armature of a magnet in the technical terminology), which is moved by the proportional solenoid in a pole tube 20. The proportional solenoid is actuated by means of a computer unit (not shown in detail) and an associated sensor system. Such an actuation is common for flow control valves, so that there is no need to enter into further details at this point. The pressure detecting chamber 12 is arranged between a guide piece 21 for the pressure detecting piston 9 and a pole tube base 22. The pressure detecting piston 9 penetrates with a widened region having a diameter D the guide piece 21, which forms a kind of rigid axially sliding bearing for the pressure detecting piston 9. The guide piece 21 and the pole tube base 22 are secured in the valve housing 2 in a sealing manner. The pressure detecting piston 9 extends through the control piston 3 with a diameter that gradually decreases downward, when viewed in the direction of FIG. 1. The pressure detecting duct 11 is formed centrally, in an axially centered manner, preferably in the form of a drill hole, which empties into at least two radially extending tap holes 23. The pressure detecting piston 9 has an additional difference in diameter 15 at the opening 18 of the drive plate 13, so that the diameter D, which said piston has in its region guided by the guide piece 21, decreases to the diameter at the opening 18.

This decrease in diameter allows a positive locking engagement of the pressure detecting piston 9 and a connection to the control piston 3. The connection is implemented in such a way that it is possible for the control piston 3 to move relative to the pressure detecting piston 9. At the same time, the resetting device 17 pushes the control piston 3 against the difference in diameter 15 of the pressure detecting piston 9 by means of the drive plate 13, against which the control piston 3 rests loosely with its outer circumference, so that such pistons 3, 9 are held permanently in engagement with each other in any position of movement.

An additional difference in diameter 15′ is present at the pressure detecting piston 9 inside its region in the control piston 3. In this case, the outside diameter of the pressure detecting piston 9 decreases to its smallest size d, so that it projects as a hollow needle in the direction of the fluid inlet 5. In the initial position, the pressure detecting piston 9 can be loaded with a predefinable actuating force on its pressure detecting chamber-side end by a tappet 25, which is connected to the armature 8 by means of a setting thread 24.

A kind of pressure compensator is formed by means of the arrangement of the pressure detecting piston 9 with the control piston 3. The side of the control piston 3 that faces the fluid inlet 5, has a correspondingly high pressure upstream of the metering orifice 14. This high pressure passes over into a comparatively lower pressure value due to the metering orifice 14 and is available at the rear side of the control piston 3 and is correspondingly available on the side of the drive plate 13 that faces away from the fluid inlet 5 due to an engagement slot (opening 18), which is not shown in detail, on the drive plate 13. If the proportional solenoid is suitably energized, then the resetting device 17, which is formed as the compression spring, is at least partially compressed.

In this embodiment of the electromagnetic flow control valve 1, the pressure that prevails in the pressure detecting chamber 12 and which is also available at the pressure-effective control surfaces of the pressure detecting piston 9 by way of the pressure detecting drill hole 11 and the tap holes 23 supports the force effect of the proportional solenoid with a force F in the same direction as the actuating force of the proportional solenoid. This force relief allows the use of a proportional solenoid that is smaller in size than is the case in the prior art solutions that dispense with the pressure detecting piston 9 according to the invention. Furthermore, such a relief is energy saving, because the power consumption for the proportional solenoid is less. Therefore, in this respect the largest cross section of the pressure detecting piston 9 decreases the projection surface of the control piston 3; and the resulting remaining control surface leads to the force introduction that reduces the load on the proportional solenoid.

The respective outflow opening 6, 6′ forms with the respective passage opening 19, 19′ assigned to each other the control orifices of the flow control valve 1. Owing to the play-restricted tappet guide for the tappet 25 in the pole tube base 22 and owing to a passage drill hole in the magnet armature 8, the pressure prevailing in the pressure detecting chamber 12 is also available at the armature 8 in a pressure compensating manner. This feature guarantees a smooth operation of the armature/tappet arrangement. The armature 8, guided in the pole tube 20, is provided outward in the conventional manner with a closure cap 26, which is connected to the pole tube 20 of the flow control valve 1 in the manner of bead.

FIG. 2 shows an additional design variant of the electromagnetic proportional directional flow control valve 1, where the key components of the flow control valve 1 and, in particular, the components installed in its valve housing 2 are more or less identical to those of the embodiment depicted in FIG. 1. Therefore, the same reference numerals and the related statements, which have already been provided for this purpose, apply to the identical components. However, in contrast to the exemplary embodiment shown in FIG. 1, the armature 8 does not act here on the pressure detecting piston 9 in a pushing manner, but rather it acts in a pulling manner in the direction of releasing a displacement path provided for the control piston 3. Therefore, in the embodiment of the flow control valve 1 shown in FIG. 2, a switching position of the control piston 3 is shown that is partially open in relation to the fluid-conducting connection 4. In this case, the proportional solenoid (not shown in detail) is not energized.

According to the drawing in FIG. 2, the pressure detecting piston 9 is pushed, in the viewing direction of the observer, downward with the control piston 3 and, in particular, subject to the action of a compression spring 27, which forms the resetting device 17 in the exemplary embodiment that is shown and exerts a force on the armature 8 of the magnet. The resetting device 17, according to FIG. 1, is designated as 17′ and is also present. In this case, the spring force of the compression spring 17′ is smaller than the spring force of the compression spring 27, so that in this respect the compression spring 17′ only has the function of “clamping” the control piston 3 without play in its respective control position. In this case, the armature rests against a bottom end stop 28 in the lowest position of movement. In order to adjust the actuating force of the compression spring 27, there is an adjusting spindle 29, which is guided in a rotatable manner in the valve arrangement by means of a setting thread 24. In addition, the upper free end of the spindle 29 is closed with a kind of venting screw 30, which engages with a screw segment 31 in an assigned internal thread at the free end of the adjusting spindle 29. Such an arrangement allows the so-called dead current to be adjusted by means of the thread under discussion. In the illustrated movement position of the control piston 3, the fluid-conducting connection 4′ is blocked; and the fluid-conducting connection 4 is partially opened. If the fluid pressure in the fluid inlet 5 increases, then the pressure-effective surfaces in conjunction with a controlled energizing of the proportional solenoid move the armature 8 upward, when viewed in the direction of FIG. 2. As a result, the overlapping area of the passage opening 19′ with the outflow opening 6′ increases; and at the same time the overlapping area of the passage opening 19 with the outflow opening 6 decreases. 

1. A flow control valve, in particular in the form of an electromagnetic proportional directional flow control valve (1), having a valve housing (2), in which a control piston (3) is guided in such a way that it can be displaced axially, and said control piston actuates at least one fluid-conducting connection (4) between a fluid inlet (5) and an outflow opening (6), wherein an actuator part, in particular an armature (8), which can be actuated by an actuator, in particular in the form of a proportional solenoid, acts on the control piston (3), characterized in that a pressure detecting piston (9) serves for the action of the actuator part on the control piston (3); that the fluid inlet (5) is connected in a fluid-conducting manner to a pressure detecting chamber (12) by means of a pressure detecting duct (11) in such a way that the fluid pressure, which prevails in the pressure detecting chamber (12), applies a force (F) to the pressure detecting piston (9) and the control piston (3) in the direction of a relief of the actuator; and that an additional fluid-conducting connection (4′) between the fluid inlet (5) and an additional outflow opening (6′) is actuated.
 2. The flow control valve according to claim 1, characterized in that when the free flow cross section of the one outflow opening (6; 6′) is enlarged, the free flow cross section of the respectively other outflow opening (6; 6′) is decreased by means of the control piston (3).
 3. The flow control valve according to claim 1, characterized in that for the purpose of a design as a kind of priority valve, the one outflow opening (6) forms a fluid port in order to supply a connectable consumer of higher priority with the fluid; and, in contrast, the other outflow opening (6′) forms an additional fluid port in order to supply a consumer of lower priority.
 4. The flow control valve according to claim 1, characterized in that the control piston (3) has at least two rows of passage openings (19, 19′) that are spaced axially apart from each other; and that one of the rows is assigned the one outflow opening (6); and a respectively other row is assigned the other outflow opening (6′).
 5. The flow control valve according to claim 1, characterized in that the passage openings (19, 19′) and the outflow openings (6, 6′) consist of a plurality of rows of drill holes assigned to each other, which are axially spaced relative to the longitudinal or actuating axis of the valve (1); and said drill holes, which are divided into rows, are arranged in such a way that they lie diametrically opposite each other.
 6. The flow control valve according to claim 1, characterized in that the control surfaces of the control piston (3), to which fluid pressure is effectively applied, and the control surfaces of the pressure detecting piston (9) yield, when pulled away from each other, a remaining control surface, to which fluid pressure is applied and that introduces a force to the two pistons (3, 9), so that the result is a relief for the proportional solenoid.
 7. The flow control valve according to claim 1, characterized in that the pressure detecting duct (11) produces a permanently fluid-conducting connection between the fluid inlet (5) and the pressure detecting chamber (12); that, for this purpose, the pressure detecting duct (11) axially penetrates the pressure detecting piston (9); and/or that, for this purpose, the pressure detecting duct (11), arranged laterally in the valve housing (2), is guided past the control piston (3).
 8. The flow control valve according to claim 1, characterized in that the pressure detecting piston (9) at least partially penetrates the control piston (3); and that the pressure detecting piston (9) defines a metering orifice (14) with a passage opening of the control piston (3) in the area of the free front side of the pressure detecting piston.
 9. The flow control valve according to claim 1, characterized in that the metering orifice (14) is formed by means of the inner wall parts of the control piston (3); and said metering orifice may be found between the outflow openings (6, 6′) in any movement position of the control piston (3); and that the pressure detecting duct (11) of the pressure detecting piston (9) extends through the metering orifice (14) so as to form a radial distance.
 10. The flow control valve according to claim 1, characterized in that the free front-side end of the pressure detecting duct (11) empties into the other fluid-conducting connection (4′) between the fluid inlet (5) and the other outflow opening (6′) in any movement position of the control piston (3).
 11. The flow control valve according to claim 1, characterized in that the armature (8), which can be axially displaced by means of the proportional solenoid, acts permanently on the control piston (3) by means of the pressure detecting piston (9), as an intermediate member.
 12. The flow control valve according to claim 1, characterized in that the pressure detecting piston (9) is loosely connected to the control piston (3) by means of a drive plate (13).
 13. The flow control valve according to claim 1, characterized in that the proportional solenoid is designed in the manner of a pushing magnet; and that when said proportional solenoid is in its non-energized state, the control piston (3) is moved by means of a resetting device (17) into a position in which the fluid-conducting connection (4) is blocked and the other fluid-conducting connection (4′) is at least partially opened.
 14. The flow control valve according to claim 1, characterized in that the proportional solenoid is designed in the manner of a pulling magnet, and that when said proportional solenoid is in its non-energized state, the control piston (3) is moved by means of a resetting device (17) into a position in which the fluid-conducting connection (4) is at least partially open and the other fluid-conducting connection (4′) is blocked. 